"Cardiovascular outcomes are also important because those with chronic kidney disease have a much higher risk of cardiovascular disease, and therefore it's important to look at both. And in [this] trial, the drug was particularly effective in cardiovascular disease at baseline," he added.

For many years in diabetes research, new drugs were tested simply for how they affected HbA1c, but after 2008, the FDA "changed the rules and asked for [other] outcomes," Mann said. As a result, liraglutide, a GLP-1 agonist, was studied for various results, including cardiovascular outcomes, which have already been published, and for renal outcomes, the focus of the current trial.

The trial, known as LEADER [Liraglutide Effect and Action in Diabetes: Evaluation of Cardiovascular Outcome Results] was a randomized controlled trial involving 9,340 diabetes patients with a high risk of cardiovascular disease. Patients were included in the trial if they had type 2 diabetes with an HbA1c of 7.0% or greater, were antidiabetic drug-naïve, took oral antidiabetic drugs and/or basal/premix insulin, and were either 50 or older with established cardiovascular disease and chronic renal failure, or 60 or older with risk factors for cardiovascular disease.

Exclusion criteria included type 1 diabetes; use of GLP-1 receptor agonists, DPP-4 inhibitors, pramlintide, or rapid-acting insulin; and a family or personal history of multiple endocrine neoplasia type 2 or medullary thyroid cancer.

Participants were injected daily subcutaneously with either 0.6-1.8 mg of liraglutide or with placebo; minimum duration was 3.5 years and maximum was 5 years, Mann said. Patients were followed for a mean of 3.8 years.

Results from the cardiovascular portion of the trial showed that liraglutide reduced cardiovascular outcomes and also all-cause death, with 1,300 cardiovascular outcomes and more than 800 deaths, he noted.

The key renal outcome was also composite -- development of macroalbuminuria, doubling of serum creatinine, end-stage renal disease (ESRD), or renal death. There were 605 renal outcomes in total. "Here again, the reduction in risk was 22%, which was significant," Mann said.

As to what drove that outcome, it was likely the reduction in macroalbuminuria, he continued. "The other components were not significantly affected," such as the doubling of serum creatinine or the need for dialysis.

The researchers also looked at some changes in estimated glomerular filtration rate (eGFR). "That is important, because for the whole group, the decrease in filtration rate was slower with liraglutide than with placebo," he said. The drug also was not associated with any increased risk of renal adverse events.

Joel Topf, MD, of St. Clair Nephrology Research in Detroit, praised the study in an email, although with some caveats. "The renal results of LEADER are solid, [but] they do not look as impressive as the results of EMPA-REG [the empagliflozin trial], which also showed a benefit in renal outcomes for a drug for type 2 diabetes," he wrote.

"My hesitancy in fully embracing the results of LEADER is that the primary outcome was met on the back of a composite outcome of doubling of serum creatinine, new ESRD, death or new macroalbuminuria," he continued. "The first three are all outcomes that patients care (or should care) about, but the last is a soft outcome."

"Making that more important is that the significant P-value for the primary outcome was largely driven by this last outcome," Topf noted. "Doubling of serum creatinine and ESRD were not significant."

Although liraglutide's renal outcomes were not quite as impressive as those of empagliflozin (Jardiance), "empagliflozin is limited to patients whose renal function is largely intact, while [liraglutide] can be used in patients with decreased renal function," Topf noted.

Overall, "This is an important study with positive implications for our patients," he concluded. "It is refreshing to see diabetic medications being tested for their effect on survival renal outcomes rather than the ability to improve HbA1c."

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